Aqueous inks, i.e. inks comprising an aqueous medium are known in the art. These inks may be applied onto a recording medium, such as paper, by jetting droplets of the ink onto the recording medium. A problem associated with jetting droplets of an aqueous ink onto a recording medium is the so called puddling phenomena: several drops tend to combine to bigger puddles in a non-controllable way. The occurrence of puddling results in visual decrease of the print quality. To prevent puddling, the droplets of ink have to be immobilized on the recording medium shortly after the droplet has been applied onto said medium. There are a number of possibilities to immobilize the droplets, such as precipitating the colorant using a primer, or by pinning the droplet. Pinning of the droplet may be effectuated by a so-called pinning agent. A pinning agent is a component that immobilizes the droplet by increasing its viscosity. In this way, displacement of the droplet is prevented.
A pinning agent may be e.g. a thermogelation additive. A thermogelation additive is a component that can be added to an ink composition and that gels the ink composition at an elevated temperature. An example of such thermogelating pinning agent is known from U.S. Pat. No. 8,318,853. However, there is a need for alternative thermogelating pinning agents for aqueous inks.
Therefore, it is an object of the present invention to provide an alternative pinning agent. It is a further object to provide an ink composition comprising such pinning agent.